ParticleEmitter.ClearParticles  

particleEmitter.ClearParticles();

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
particleEmitter.ClearParticles();
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
particleEmitter.ClearParticles()